While there are presently available various types of automatic tools, including drill presses which are electronically and/or computer controlled to ensure precise and uniformly consistant results, such machines are costly and tend to obsolete the large numbers of drill press machines which are not equipped with such automatic control systems.
There has, thus, been a long-felt need to provide an inexpensive, simple and reliable device for retrofitting onto existing machines to significantly upgrade the performance of such machines.
In U.S. Pat. No. 2,909,082 to Booth, dated Oct. 20, 1959, a device, which can be attached to a standard drill press, is disclosed for automatically feeding or advancing the drill spindle into the work and for stopping the press upon the completion of a hole drilled to a predetermined depth. While this patent discloses a device for the automatic feed and depth control of a drill press, it requires the use of coil spring 62, that is fitted around the control bar to overpower the spring 42 that conventionally urges the spindle upwardly. A limit switch in an electrical circuit is also required to de-energize the spindle drive motor. Nothing is disclosed in the Booth patent, however, which would physically prevent turning "off" switch 31 using the handle 18 to retract the drill before a hole has been bored to its full depth. Moreover, since the force of return spring 42 is overcome by coil spring 62, the handle 18 must be used to retract the spindle and for each operating cycle, the operator would have to lock the spindle in its "up" position to set up for another cycle of operation. In addition, the length of spring 62 would substantially reduce the maximum depth of holes which could be drilled using this device.
It is the principal object of this invention to provide a mechanical quality control device of simple and inexpensive construction for attachment to existing drill presses which can be easily installed, is simple to use and which is yet highly effective to ensure that drill press operators to not retract the drill from a workpiece until each hole has been drilled to its full depth.
It is another object of this invention to provide an after-market attachment of the above type in which the component thereof most subject to wear can be readily replaced by a commonplace elastic O-ring.
It is a further object of this invention to provide an attachment of the above type which can be readily fitted onto existing drill presses without any modification thereof and which does not otherwise change the operating procedures nor performance characteristics of the press.